Survey finds that most meta-analysts do not attempt to collect individual patient data.

OBJECTIVE

To characterize current efforts and outcomes of individual patient data (IPD) collection among meta-analysts of randomized controlled clinical trials.

STUDY DESIGN AND SETTING

Corresponding authors of meta-analyses of randomized controlled trials in general medicine with a binary endpoint were sent an e-mail survey inquiring about their efforts to obtain IPD. Descriptive statistics of each meta-analysis were extracted to evaluate their association with data seeking.

RESULTS

Only 22 (4.2%) of the sampled meta-analyses included IPD. Of the 360 authors surveyed, 256 (71%) reported not seeking IPD: 48% thought that the undertaking would be too difficult, 30% thought that it was not necessary for their main analysis, 25% did not have sufficient time or resources, and 22% never considered it. Seeking IPD was not significantly associated with any trial characteristic examined, including whether subgroup analyses were performed. Authors who sought IPD obtained a median of two data sets (interquartile range=0-5). Unsuccessful contact (43%), refusal without explanation (21%), and lost or inaccessible data (20%) were the most common reasons why trial data could not be obtained.

CONCLUSION

The infrequency of attempts made by meta-analysts to obtain participant data is an important contributor to the rarity of IPD meta-analyses.